It's a simple thing, when you rush a project, you're generally not going to give it your best effort. Corners are cut, things are left out.
When that project is a multi-trillion dollar new entitlement set to re-shape healthcare for the entire nation, haste is a disaster. The bill that was passed was introduced and rushed to a vote with little to no debate in both the house and the senate. Haste in this case, is a nightmare.